1. Field of the Invention
The present invention relates to a method and apparatus for use in producing a cathode ray tube, more particularly to a method and apparatus for fabricating a fluorescent screen at the inner surface of a cathode ray tube panel.
2. Description of the Related Art
One well known conventional method of fabricating a fluorescent screen at the inner surface of a cathode ray tube panel is the so-called "slurry method". The slurry method involves coating of a phosphor slurry followed by drying, exposure and development, washing and removal, and other steps. The facilities required therefore become large in size and the work becomes complicated.
Therefore, other methods such as electro-deposition and heat transfer have been proposed.
In the electro-deposition method,.however, the entire surface of the panel is immersed in an electro-deposition tank, so phosphors deposit at portions other than the intended fluorescent screen as well. Removal of this requires washing, wiping, and other work. If phosphors remain at the unnecessary portions, then the unnecessary portions will fluoresce when irradiated by a beam.
Electro-deposition also requires the provision of an electro-conductive film (for example, a metal-back layer such as vapor-deposited aluminum film etc.) as an underlayer at the inside surface of the panel. Further, it requires terminals for the conduction of power at the time of electro-deposition.
Further, the heat transfer method requires a heat transfer film comprised of a base film, a separation layer, a phosphor layer, and an adhesion layer. It also requires a step of heat transfer printing on the inner surface of a curved panel using this heat transfer film. Accordingly, the process is complicated and the manufacturing costs become high. After the heat transfer printing, further, a step of burning off the resin component included in the separation layer and the adhesion layer is required. Therefore, there are a large number of steps and there is a danger of dust and other foreign matter depositing on the fluorescent screen and thereby the quality of the fluorescent screen becoming unstable.
Therefore, attempts have been made to fabricate a fluorescent screen on the inner surface of the panel by screen printing.
The screen used for screen printing, however, as shown in FIGS. 1A and 1B, is a flat-stretched screen 2. The screen frame 3 gets in the way and therefore it is not possible to print on the inner surface of the curved panel. Note that the screen 2 shown in FIGS. 1A and 1B has a transfer pattern 1 formed at its center. By moving a squeegee 4 along the surface of the screen 2, the ink 5 is spread and the pattern 1 is transferred to the work.